Reporting power headroom for aggregated carriers

ABSTRACT

A method for reporting power headroom-related information for a plurality of aggregated carriers. The method includes reporting in a bitmap the power headroom-related information for a number of the aggregated carriers that is less than or equal to the total number of aggregated carriers, wherein the power headroom-related information is one of a power headroom for at least one of the aggregated carriers and a path loss for at least one of the aggregated carriers.

BACKGROUND

As used herein, the terms “user agent” and “UA” might in some casesrefer to mobile devices such as mobile telephones, personal digitalassistants, handheld or laptop computers, and similar devices that havetelecommunications capabilities. Such a UA might consist of a device andits associated removable memory module, such as but not limited to aUniversal Integrated Circuit Card (UICC) that includes a SubscriberIdentity Module (SIM) application, a Universal Subscriber IdentityModule (USIM) application, or a Removable User Identity Module (R-UIM)application. Alternatively, such a UA might consist of the device itselfwithout such a module. In other cases, the term “UA” might refer todevices that have similar capabilities but that are not transportable,such as desktop computers, set-top boxes, or network appliances. Theterm “UA” can also refer to any hardware or software component that canterminate a communication session for a user. Also, the terms “useragent,” “UA,” “user equipment,” “UE,” “user device” and “user node”might be used synonymously herein.

As telecommunications technology has evolved, more advanced networkaccess equipment has been introduced that can provide services that werenot possible previously. This network access equipment might includesystems and devices that are improvements of the equivalent equipment ina traditional wireless telecommunications system. Such advanced or nextgeneration equipment may be included in evolving wireless communicationsstandards, such as long-term evolution (LTE). For example, an LTE systemmight include an Evolved Universal Terrestrial Radio Access Network(E-UTRAN) node B (eNB), a wireless access point, or a similar componentrather than a traditional base station. As used herein, the term “accessnode” will refer to any component of a wireless telecommunicationssystem, such as a traditional base station, a wireless access point, oran LTE eNB, that creates a geographical area of reception andtransmission coverage allowing a UA to access other components in thesystem. An access node may comprise a plurality of hardware andsoftware.

LTE was standardized in Release 8 of the wireless telecommunicationsstandards promoted by the 3rd Generation Partnership Project (3GPP).3GPP Release 10 standards deal with LTE-Advanced or LTE-A technology.Under LTE-A, relays and other advanced components might be included in awireless telecommunications network. A relay is a component in awireless network that is configured to extend or enhance the coveragecreated by an access node or another relay. Although access nodes andrelays may be distinct components with different capabilities andfunctions, for ease of reference, the term “access node” will be usedherein to refer to either a relay or an access node as described above.

The signals that carry data between UAs, relay nodes, and access nodescan have frequency, time, and coding parameters and othercharacteristics that might be specified by a network node. A connectionbetween any of these elements that has a specific set of suchcharacteristics can be referred to as a resource. The terms “resource,”“communications connection,” “channel,” and “communications link” mightbe used synonymously herein. A network node typically establishes adifferent resource for each UA or other network node with which it iscommunicating at any particular time.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 illustrates an aggregation of carriers.

FIG. 2 illustrates a procedure by which an access node grants a resourceto a user agent.

FIG. 3 is a diagram of a power headroom and related quantities.

FIG. 4 is a diagram of a control element that could be used fortransmitting power headroom-related information according to anembodiment of the disclosure.

FIG. 5 a is a diagram of a control element that could be used fortransmitting power headroom-related information according to analternative embodiment of the disclosure.

FIG. 5 b is a diagram of a control element that could be used fortransmitting power headroom-related information according to analternative embodiment of the disclosure.

FIG. 6 is a diagram of a control element that could be used fortransmitting power headroom-related information according to analternative embodiment of the disclosure.

FIG. 7 is a table showing a mapping between a power difference and atwo-bit variable according to an embodiment of the disclosure.

FIG. 8 is a table illustrating a calculation of a power differencebetween a carrier and a reference carrier according to an embodiment ofthe disclosure.

FIG. 9 is a diagram of a control element that could be used fortransmitting power headroom-related information according to analternative embodiment of the disclosure.

FIG. 10 is a diagram of a control element that could be used fortransmitting power headroom-related information according to analternative embodiment of the disclosure.

FIG. 11 illustrates an exemplary MAC control element according to anembodiment of the disclosure.

FIG. 12 is a diagram illustrating a method for reporting powerheadroom-related information for a plurality of aggregated carriersaccording to an embodiment of the disclosure.

FIG. 13 illustrates a processor and related components suitable forimplementing the several embodiments of the present disclosure.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents.

In LTE-A, carrier aggregation might be used in order to support widertransmission bandwidths and hence increase the potential peak data rateto meet LTE-A requirements. In carrier aggregation, multiple componentcarriers are aggregated and can be allocated in a subframe to a UA asshown in FIG. 1. In this example, each component carrier 110 has a widthof 20 MHz and the total system bandwidth becomes 100 MHz. The UA mayreceive or transmit on a multiple of up to five component carriersdepending on its capabilities. In addition, depending on the deploymentscenario, carrier aggregation may occur with carriers located in thesame band and/or carriers located in different bands. For example, onecarrier may be located at 2 GHz and a second aggregated carrier may belocated at 800 MHz.

In uplink transmissions, a UA transmits a power headroom report (PHR)and a buffer status report (BSR) to an access node in order to assistwith uplink scheduling. The access node uses this information when itdetermines the amount of frequency resources and proper modulation andcoding scheme (MCS) level for physical uplink shared channel (PUSCH)transmissions. FIG. 2 shows the general flow of an uplink transmissionfrom a UA 210 to an access node 220. When new data arrives at the UAbuffer, the UA 210, at event 231, transmits a scheduling request on thephysical uplink control channel (PUCCH) if there is no uplink PUSCHresource available for the initial transmission. Since the access node220 does not know the current uplink channel conditions or the amount ofpending data, the access node 220 schedules a small amount of uplinkresources, as shown at event 232. The UA 210, at event 233, thentransmits a PHR and BSR using this initial uplink resource. With thisadditional information, the access node 220, at event 234, can providethe UA 210 with a larger amount of uplink resources. At event 235, theUA 210 transmits to the access node 220 at a higher data rate accordingto the UA buffer status and the observed channel conditions.

As shown in FIG. 3, the power headroom (PH) 310 is defined as thedifference between the nominal UA maximum transmit power (P_(cmax)) 320and the estimated power for PUSCH transmissions (P_(pusch(i))) 330. Evenwhen the same data rate is transmitted in two different situations, thePH values can be different depending on the current UA channelconditions. From the access node scheduler's point of view, a large PHmeans that the UA has more room to increase its power to accommodate ahigher data rate transmission, while a small PH means that the UA cannotincrease its data rate.

The 3GPP Technical Specification (TS) 36.213, which is incorporatedherein by reference for all purposes, defines the following equationwhich a UA can use to calculate the PH:

$\begin{matrix}{{{PH}(i)} = {P_{CMAX} - {P_{PUSCH}(i)}}} \\{= {P_{CMAX} - \left\{ {{10{\log_{10}\left( {M_{PUSCH}(i)} \right)}} + {P_{O\_{PUSCH}}(j)} +} \right.}} \\\left. {{{\alpha(j)} \cdot {PL}} + {\Delta_{TF}(i)} + {f(i)}} \right\}\end{matrix}$

This equation means that the PH is the remaining available transmissionpower, obtained by subtracting the uplink transmission power at the ithsubframe from the maximum allowable transmission power. The parametersare defined as follows.

-   -   P_(CMAX) is the configured maximum UA transmission power.    -   M_(PUSCH)(i) is the bandwidth of the PUSCH resource assignment        expressed in number of resource blocks scheduled for subframe i.    -   P_(O) _(—) _(PUSCH)(j) is a parameter composed of the sum of a        cell-specific nominal component and a UA-specific component        provided by higher layers.    -   a(j) is defined in 3GPP TS 36.213.    -   PL is the downlink path loss estimate calculated in the UA in        dB.    -   Δ_(TF)(i) is the offset with respect to the transport format.    -   f(i) is the power control adjustment.

In LTE-A systems, UAs might report their PH to an access node to assistwith uplink scheduling as in the case with LTE systems. However, the PHreporting approach used in LTE, where PH is the difference between themaximum allowable and current uplink transmission powers, may not beappropriate in LTE-A. An LTE-A UA is able to transmit using multiplecarriers simultaneously, and scheduling might be performed on aper-carrier basis with different MCS levels. If each carrier isconstrained to use the same uplink transmit power, one PH report may besufficient. However, the uplink transmit power would be expected to bedifferent for each carrier because some power-related parameters mightvary for different carriers.

For example, the path loss can be different if the carriers are locatedin different bands. Assuming two example carriers are located at 2 GHzand 800 MHz, respectively, the expected statistical difference in pathloss can be calculated as a function of the frequency based on the pathloss model in 3GPP Technical Report (TR) 25.942. In this model, the pathloss L is given as 40(1−4×10⁻³ Dhb) Log₁₀(R)−18 Log₁₀(Dhb)+21Log₁₀(f)+80 dB, where f is the frequency in MHz, Dhb is the access nodeantenna height in meters (in 3GPP, 15 m is assumed), and R is thedistance between the access node and the UA in kilometers. For 2 GHz,L=128.1+37.6 Log₁₀(R). For 800 MHz, L=119.7+37.6 Log₁₀(R). So, providedthat there are no other factors, the expected mean difference in pathloss between 2 GHz and 800 MHz will be about 9 dB. It is noted that thisdifference has been calculated with a statistical model. In an actualdeployment, it would be not be realistic for an access node to be ableto accurately predict the path loss difference between bands due todifferent propagation characteristics as a function of the frequency.For example, higher frequency carriers generally attenuate faster as afunction of distance and are also more likely to be attenuated byenvironmental factors such as building penetration, foliage, rain, etc.

Also, the power control adjustment, f(i), might be different fordifferent carriers. An access node could transmit individual TPC(Transmit Power Control) commands per carrier or a single combined TPCcommand for all of the carriers. Even though the access node originatesthe TPC commands, it would be difficult for the access node to correctlytrack the current f(i) values per carrier due to possible TPC signalingerrors and/or TPC signals that were mis-detected by the UA.

In addition, P_(O) _(—) _(PUSCH) might vary for different carriers.P_(O) _(—) _(PUSCH) is a cell- and UA-specific parameter that adjuststhe target signal to interference-plus-noise ratio (SINR) based on theinterference level. Since each component carrier is scheduledindependently, each carrier might experience a different inter-cellinterference level. The loading of different carriers may be differentdepending on the scheduling in the neighbor cells. For example, theaccess node might schedule cell-edge UAs on one carrier and morecentrally-located UAs on the remaining carriers. In addition, thenetwork topology may result in different neighboring cells havingdifferent carriers available. For instance, one cell may have fivecarriers in total, but a neighboring cell that is expected to be lesslightly loaded may only be configured with a maximum of three carriers.

Also, a(j) might be different for different carriers. a(j) is acell-specific parameter intended to improve cell throughput under smallinterference levels. This parameter can be varied based on the cellloading and/or on the UA distribution within a cell.

For these and other reasons, the uplink transmit power, and thereforethe power headroom, might be different for each carrier in a set ofaggregated carriers. To reflect the need for individual PH values percarrier or per band, the PH of all carriers could be reported to theaccess node. However, this could result in excessive signaling overhead,since it may not be necessary to report the PH for every carrier. In anembodiment, various schemes are provided for efficiently transmittingper-carrier PH values for a set of aggregated carriers in order toreduce signaling overhead.

Most of the factors determining a PH value are carrier-specific but,other than path loss (and possibly the current power controlcorrection), the access node is typically aware of these parameters.Therefore, if the access node is made aware of the path loss for eachcarrier, the access node can calculate a PH for each carrier. A UA couldreport an observed path loss in a higher-layer measurement report, butsuch a report may not be sent frequently enough because higher-layermessages tend to be larger and generally incur some delay before beingtriggered. Consequently, it may be advantageous for the UA to report aseparate PH value to the access node for each carrier. However, it maybe unnecessary to report separate PH values for all carriers given thatthe path losses of carriers located in the same frequency band aretypically similar.

In an embodiment, to avoid additional signaling overhead, the number ofcarriers for which the PH or PH-related information is reported is lessthan or equal to the total number of configured carriers. For notationalconvenience, a carrier for which a PH or PH-related information isreported is referred to herein as a “reporting carrier”. In anembodiment, there are two approaches to configure which carriers arereporting carriers.

In one embodiment, a UA determines which carriers are reporting carriersbased on whether the carriers are located in the same band or not. If aPH report has been triggered by one of the triggering criteria describedbelow, and if there are multiple carriers in the same band, the UA canselect the reporting carrier using a predefined set of rules known byboth the access node and UA. For example, the UA might choose thecarrier having the lowest centre frequency, the carrier having thelowest physical cell ID, or some other carrier or carriers. Since theaccess node already knows whether or not the configured carriers arelocated in the same band, the UA does not have to signal its decision tothe access node. The access node is aware of this predefined rule andcan utilize the PH reporting correctly.

In another embodiment, an access node configures the carrier set to bereported. The access node selects the carriers for which PH reportingwill be performed and communicates this decision to the UA via radioresource control (RRC) signaling or media access control (MAC) controlelements. This approach provides additional freedom to the access nodebecause the access node can select the reporting carriers regardless ofwhether those carriers are located in the same or different bands. Oneapproach would involve the access node using a bitmap to indicate whichcarriers' PHs should be reported, although other methods could also beused.

In LTE, a PH report might be transmitted at periodic intervals and/orwhen a triggering event occurs. According to 3GPP TS 36.321, a PH reportis triggered if any of the following events occur: the prohibitPHR-Timerexpires or has expired and the path loss has changed more thandl-PathlossChange dB since the last power headroom report, when the UAhas uplink resources for a new transmission; the periodicPHR-Timerexpires, in which case the PHR is referred to as a “Periodic PHR”; uponconfiguration and reconfiguration of a Periodic PHR.

In an embodiment, these criteria are expanded to support carrieraggregation under LTE-A. The triggers related to the expiration of theperiodicPHR-Timer and the configuration and reconfiguration of aPeriodic PHR might remain the same, but the trigger related to theexpiration of the prohibitPHR-Timer might be modified. Morespecifically, in LTE-A, a PH report is triggered if theprohibitPHR-Timer expires or has expired and the path loss of anyreporting carrier has changed more than dl-PathlossChange dB since thelast power headroom report, when the UA has uplink resources for a newtransmission. The PH reporting scheme could be such that only reportingcarriers that satisfy this dl-PathlossChange criterion actually reporttheir new PH values. That is, not all configured reporting carrierswould actually include their PH values in the PH report.

It has been discussed that the number of active carriers currently usedby a UA can be configured semi-statically. In this case, when a newcarrier is added to an aggregation of carriers, it may be desirable toreport its PH as soon as possible to assist with uplink scheduling onthat carrier. Therefore, in an embodiment, as one additional criterionfor LTE-A PH reporting, a PH report is triggered when a UA receives anew carrier configuration from the access node and/or a new PH reportingconfiguration that includes a new reporting carrier.

As mentioned previously, a UA could transmit a PH report to an accessnode via RRC signaling or via MAC control elements. Since the RRCsignaling approach might incur additional delay and signaling overhead,the MAC control element approach may be preferable. The followingalternatives for transmitting a PH or PH-related information are basedon the MAC control element approach. If there is no explicit indicationotherwise, the PH reporting discussed in the following alternatives istriggered according to the criteria described above.

In one alternative, when PH reporting is triggered, a UA transmits thePHs for all of the reporting carriers. For example, if there are fourreporting carriers, when the observed path loss difference for one ofthe reporting carriers exceeds the configured threshold (that is, thepath loss of a reporting carrier has changed more than dl-PathlossChangedB), the UA transmits the PHs for all four of the reporting carriers.

FIG. 4 illustrates an example of a MAC control element 400 that could beused for transmitting the PHs of all reporting carriers. The controlelement 400 consists of three byte-aligned octets 410. The number of PHvalues equals the number of reporting carriers. In this example fourreporting carriers have been configured. The length of the PH values issix bits, as in LTE. Each PH_(k) represents the PH of carrier k. In someembodiments, if the allocated UL resources cannot accommodate the MACcontrol element of all PHs plus its subheader as a result of logicalchannel prioritization, then the UA can decide not to transmit all PHsor transmit PHs of a subset of carriers in the MAC control element to beaccommodated in the allocated UL resources. The UA can select carriersbased on the logical or physical carrier indexing. In one embodiment,the UA can select a carrier based on the priority of the carrier. Forexample, the UA can transmit the PH of the uplink anchor carrier or acarrier used to transmit data with a high quality of service (QoS).

In another alternative, a UA transmits a PH report in a long format or ashort format depending on the situation. That is, to reduce signalingoverhead, two different kinds of PH report can be defined: a wideband PHreport and a per-carrier PH report. The wideband PH report representsthe power situation across the system bandwidth and could be generatedby averaging the PH values of all carriers, could include the PH of acertain representative carrier, or could represent the system-wide powerin some other manner. This wideband PH report could be transmitted in aMAC control element, and the existing LTE format could be re-usedbecause the wideband PH report includes only one PH value. Forper-carrier PH reports, the PH of each carrier could be transmitted asdescribed above.

When these two different PH reports are used, the PH reports could beconfigured using one of two different techniques. In one technique,different reporting periodicities are configured for each type ofreport, with the wideband PH being reported more often than theper-carrier PHs. For example, a wideband PH might be reported every 10milliseconds, and per-carrier PHs might be reported every 100milliseconds. In another technique, whenever a PH report is to begenerated, the UA transmits per-carrier PH information if the PHdifference between different reporting carriers or the differencebetween per carrier PHs and the wideband PH are larger than a presetthreshold. Otherwise, the UA transmits a wideband PH report. Thisthreshold could be configured by higher-layer signaling. When thissecond technique is used, the UA could indicate whether the PH report isof the wideband or per-carrier PH format by including a 1-bit indicatorbefore the PH values.

Sample control element formats that could be used in the secondtechnique are shown in FIGS. 5 a and 5 b. In both cases, the controlelements consist of byte-aligned octets, the length of the PH values issix bits, and reserved bits and/or padding bits can be used for bytealignment. In the wideband PH control element 500 of FIG. 5 a, a one-bitindicator 510 is included at the beginning of the control element 500.One value for this indicator 510, for example “1”, indicates that thiscontrol element 500 includes only a wideband PH. A padding bit 520 isthen included, and then a PH value 530 that represents the powersituation across the system bandwidth is included.

In the per-carrier PH control element 550 of FIG. 5 b, the one-bitindicator 510 is again included at the beginning of the control element550. The alternative value for this indicator 510, “0” in this example,indicates that this control element 550 includes PH values for allreporting carriers. A padding bit 520 is then included, followed by thePH values 560 for the reporting carriers in a manner similar to thatdepicted in FIG. 4. Additional padding bits 520 then fill out the lastoctet.

In another alternative, a UA transmits the PH value for one carrier andPH-related information for the remaining carriers at the same time. Toreduce signaling overhead, one of two techniques could be used totransmit PH information for all reporting carriers.

In one technique under this alternative, a UA transmits the PH or thepath loss of one reporting carrier. This carrier can be referred to asthe reference carrier. For the remaining reporting carriers, the UAtransmits a value representing a variation between the PH or path lossof the reference carrier and the PH or path loss of the remainingreporting carriers. That is, the UA reports the PH of the referencecarrier and the relative difference between the PHs of the othercarriers and the reference carrier's PH. Alternatively, the UA reportsthe path loss of the reference carrier and the relative differencebetween the path losses of the other carriers and the referencecarrier's path loss, and the access node then calculates the PH based onthe path loss information. The number of bits used to signal therelative differences is smaller than the number of bits used forsignaling the absolute PH or absolute path loss value, thus reducingsignaling overhead. The reference carrier could be the anchor carrier orthe carrier transmitting the current PH report. If additional signalinginformation is included, the carrier having the highest (or lowest) PHcould instead be the reference carrier.

In another technique under this alternative, a UA reports a single PHvalue and a bitmap, with the length of the bitmap equal to the number ofcarriers. If a particular carrier's bit within the bit map is one of twobinary values (for example “1”), then that carrier's power headroom isgreater than or equal to the reported PH value. If a particularcarrier's bit within the bit map is the other of two binary values (forexample “0”), then that carrier's power headroom is less than thereported PH value. This approach does not give an exact PH value foreach carrier, but may provide sufficient information for schedulingpurposes and results in fewer bits being required for power headroomreporting.

Under either of these techniques, the average PH value of all carrierscould be transmitted instead of the specific PH value of one carrier. Inthis case, the remaining carriers will include all of the reportingcarriers and the PH-related information to be transmitted will be thedifference between this average PH value and the specific PH value ofeach of these carriers.

In the first technique of this alternative, a UA transmits the PH valuefor one carrier and transmits condensed PH-related information for theremaining carriers more frequently than the rate at which full absolutePH values are reported. More specifically, an absolute PHR containing PHinformation for all of the reporting carriers can be provided at certainperiodic time intervals in order to ensure that the UA and access nodeare synchronized on this information. Between these absolute PHRs, theUA provides “incremental” PHRs that provide the absolute PH informationfor one carrier (for example, the anchor carrier or reference carrier)and relative incremental information for the remaining carriers (up tofour additional carriers). This incremental information specifies howthe path loss and power control correction of a carrier have changedrelative to the anchor carrier's path loss. This allows the remainingcarriers' PH values to be determined at the access node. The incrementalinformation reporting is triggered by the criteria described above. Inthe case of incremental reporting, a different threshold from thethreshold used for triggering an absolute PH could be configured.

There could be different ways of generating this incremental value. Inone approach, the incremental value denoted by δ_(k)(i) is calculatedfrom the path loss and power control correction difference between theanchor carrier and other carriers as follows.C _(A)(i)=a _(A)(j)·PL _(A)(i)+f _(A)(i)C _(k)(i)=a _(k)(j)·PL _(k)(i)+f _(k)(i)δ_(k)(i)=(C _(k)(i)−C _(k)(i−1))−(C _(A)(i)−C _(A)(i−1))where a_(A)(j), PL_(A)(i), f_(A)(i) are (respectively) the alpha value,path loss, and power control correction for the anchor carrier, anda_(k)(j), PL_(k)(i), f_(k)(i) are (respectively) the alpha value, pathloss, and power control correction for the carrier which reports theincremental value. The i and n indices for indicating time instances areused interchangeably in the discussion of this technique.

The UA calculates this δ_(k)(i) value and transmits the value to theaccess node. The access node then uses this signaled value to determinethe appropriate PH value for the non-anchor carriers. One approach forso doing is shown in the equation given below:

PH_(k)(n) = PH_(k)(n − 1) + (10log₁₀(M_(PUSCH, k)(n − 1)) + Δ_(TF, k)(n − 1)) − (10log₁₀(M_(PUSCH, k)(n)) + Δ_(TF, k)(n)) + PH_(A)(n) + (10log₁₀(M_(PUSCH, A)(n)) + Δ_(TF, A)(n)) − (PH_(A)(n − 1) + (10log₁₀(M_(PUSCH, A)(n − 1)) + Δ_(TF, A)(n − 1))) + δ_(k)(n)where the A subscript represents the anchor carrier, and the k subscriptrepresents the kth carrier (where k covers all of the non-anchorreporting carriers). The M_(PUSCH) and Δ_(TF) terms are added orsubtracted as appropriate to compensate for the portion of the PHcalculation that depends upon the corresponding transmission allocation(i.e., the number of allocated resource blocks and the transport blocksize). The n and n−1 indices on these quantities correspond to thetransmission allocation parameters for the subframe where the PH wascalculated. Due to Hybrid Automatic Repeat Request (HARQ)retransmissions of MAC Protocol Data Units (PDUs), this represents thesubframe where the original HARQ transmission was made. This informationcould be stored at the access node. δ_(k) is a relative incrementaladjustment described further below, which can be calculated as shownearlier.

It is recognized that the above equation is rather complicated and couldbe simplified by separating it into several different equations, such asshown in the example below.P _(A)(n)=PH _(A)(n)+(10 log₁₀(M _(PUSCH,A)(n))+Δ_(TF,A)(n))P _(k)(n)=P _(k)(n−1)+(P _(A)(n)−P _(A)(n−1))+δ_(k)(n)PH _(k)(n)=P _(k)(n)−(10 log₁₀(M _(PUSCH,k)(n))+Δ_(TF,k)(n))

The P quantities in the above equations essentially track a combinationof the path loss and power control correction for each of the carriers.

FIG. 6 shows an example format of such a Power Headroom MAC controlelement for the relative incremental reporting scheme. In thisembodiment, the MAC control element 600 includes a PH value 610 for theanchor carrier. This value 610 is substantially similar to a PH valuethat would be transmitted under LTE for a single carrier. The MACcontrol element 600 also includes a plurality of fixed length payloads620 of two bits. The payloads 620 are labeled in FIG. 6 as d_(k)(n),where different values of k represent different carriers. If less thanfive carriers are in use, one or more d_(k)(n) values are replaced bypadding bits. Each d_(k)(n) value is mapped to a δ_(k)(n) value, whereδ_(k)(n) represents a relative incremental adjustment (in dB) or a valuethat is input to a function in order to determine the appropriateadjustment that should be made to the corresponding PH value currentlybeing tracked at the access node for carrier k.

Values for δ_(k)(n) are indexed using the corresponding signaledd_(k)(n) values. An example mapping of these quantities is shown in thetable 700 of FIG. 7. Each possible value of the two-bit d_(k)(n) payload620 is mapped to a different value 710 for δ_(k)(n). In this example,the δ_(k)(n) values are −3 dB, −1 dB, +1 dB, and +3 dB, but in otherembodiments other δ_(k)(n) values could be used. If one of the payloads620 of the control element 600 has the value of “00”, for example, theδ_(k)(n) value for the corresponding carrier is −3 dB, if one of thepayloads 620 of the control element 600 has the value of “01”, theδ_(k)(n) value for the corresponding carrier is −1 dB, and so on.

The example table 800 shown in FIG. 8 may be used to illustrate thismethod. Here, there are five carriers 810, including the referencecarrier, and four other carriers (numbered from 1 to 4). The combinedpath loss and power control corrections for the previous reporting time(i.e., n−1) are shown in the second column 820, and the combined pathloss and power control corrections for the current reporting time (i.e.,n) are shown in the third column 830. As can be seen, the path loss hasgenerally increased (e.g., perhaps the UA is now shadowed by abuilding), although by a different amount for each carrier. The fourthcolumn 840 contains the delta change for each carrier from time n−1 totime n. This may be obtained by subtracting an entry in the secondcolumn 820 of the table 800 from the corresponding entry on the same rowand in the third column 830. Finally, the fifth column 850 shows thedelta value of each carrier relative to the reference carrier. Thesequantities may be obtained by subtracting the reference carrier's valuein the fourth column 840 from each carrier's delta value in the fourthcolumn 840. This essentially follows the equation defined above forδ_(k)(n). The values in this last column 850 may then be mapped tod_(k)(n) for signaling purposes as shown in table 700 of FIG. 7. If aderived δ_(k)(n) value has not been mapped to a d_(k)(n) value, a mappedδ_(k)(n) value that is close to the derived δ_(k)(n) value can be used.For example, for values where an exact match does not occur in table 700(such as 0 dB for carrier 4), the closest δ_(k)(n) from table 700 isselected.

In yet another alternative for reporting LTE-A power headroom via a MACcontrol element, a UA transmits the PH of only a certain reportingcarrier or of only certain reporting carriers. The disadvantage oftransmitting the PH for all reporting carriers, as described in thefirst alternative given above, is that PH information may be reportedunnecessarily. In an embodiment, to reduce signaling overhead, the UAtransmits PH information only for a carrier or carriers for which aspecific event trigger occurs or when that carrier's PUSCH is scheduled.Different dl-PathlossChange, periodicPHR-Timer, and/or prohibitPHR-Timercan be configured for each carrier or for a subset of carriers. In casewhere multiple events are triggered, PHs of all triggered carriers canbe transmitted. For example, when the path loss difference is largerthan a preconfigured threshold in carrier #1, UA would transmit the PHonly for carrier #1. To indicate to the access node which reportingcarriers' PHs are being transmitted, additional signaling, such as abitmap, is included with a PH report. In some embodiments, if theallocated UL resources cannot accommodate the MAC control element of allPHs plus its subheader as a result of logical channel prioritization,then the UA can decide not to transmit all PHs or transmit PHs of asubset of carriers in the MAC control element to be accommodated in theallocated UL resources. The UA can select carriers based on the logicalor physical carrier indexing. In one embodiment, the UA can select acarrier based on the priority of carrier. For example, the UA cantransmit PH of the uplink anchor carrier or carrier transmitting thehigh QoS data.

An example of this technique is shown in FIG. 9, where a MAC controlelement 900 includes a bitmap 910 with a length equal to the number ofreporting carriers. In this case, there are five reporting carriers, sothe bitmap 910 includes five bits. The bit in the k^(th) positionindicates whether or not the PH value of the k^(th) carrier is includedin the control element 900. For example, “1” may mean that thecorresponding PH value is included, while “0” may mean that the PH valueis not included. In this example, the first, fourth, and fifth bits ofthe bitmap 910 are set to “1”, so PH values for the first, fourth, andfifth carriers are included in the control element 900.

Alternatively, other reporting triggers could determine whether the PHof a reporting carrier is included in the control element 900. Forexample, an access node could specify that reporting carrier PHs are tobe included only for the carrier having the highest PH or only forcarriers having a PH larger than a specified threshold. In these cases,the number of carriers to include and/or the threshold can be predefinedor configured by higher-layer signaling.

As another technique for transmitting PH values for a subset of thereporting carriers, the UA indicates the number of reported PH valuesand a corresponding carrier index for each of the carriers transmittinga PH value. The UA transmits a consolidated power headroom report (i.e.,PH information for multiple carriers contained within a single MACcontrol element) on only one of the reporting carriers. This carrier canbe labeled as the signaling carrier. The first PH value in a reportedlist of PH values can be automatically associated with the signalingcarrier. Additional PH values in the list are then indexed using two-bitvalues to indicate which carrier they are associated with, with apre-determined order being used to link index values with carriers(e.g., in ascending order of frequency).

An example of this technique is shown in FIG. 10. The first two bits1010 of a MAC control element 1000 represent the total number of PHvalues included in the control element 1000, with the range of valuesthat can be signaled being a function of the total number of aggregatedcarriers (e.g., a range of 2-5 when five carriers are aggregated, and arange of 1-4 when less than five carriers are aggregated). The remainder1020 of the first octet includes the PH of the signaling carrier. Eachsubsequent octet includes a two-bit carrier index 1030 followed by a PH1040 for the indexed carrier. The index 1030 indicates which of theother, non-signaling carriers has the PH value in the PH portion 1040 ofthe octet. For example, if there were four non-signaling carriers, acarrier index 1030 of “00” might refer to the first non-signalingcarrier, a carrier index 1030 of “01” might refer to the secondnon-signaling carrier, and so on.

It should be noted that a combination of the above approaches can beused depending on the operation. For example, a UA might report PHvalues for all carriers periodically. Meanwhile, in the event-triggeredcase, the UA might report only for the selected carriers in order toreduce the signaling overhead.

In an embodiment, to support carrier aggregation, the calculation usedto obtain PH in an LTE-based environment is modified to becarrier-specific in an LTE-A-based environment. An example of such amodified PH equation for calculating the PH value for LTE-A is givenbelow.PH _(k)(i)=P _(CMAX,k)−{10 log₁₀(M _(PUSCH,k)(i))+P _(O) _(—)_(PUSCH,k)(j)+a_(k)(j)·PL _(k)+Δ_(TF,k)(i)+f _(k)(i)}where the definition of each parameter is given in 3GPP TS 36.213, butparameter values are different on a per-carrier basis. k denotes the kthcarrier to be reported.

With the current LTE PH equation, scheduling information is needed tocalculate PH. For example, the number of scheduled resource blocks(M_(PUSCH,k)(i)) needs to be known and the transport block size isneeded in order to calculate Δ_(TF,k)(i). In an LTE-A-based environmentwith aggregated carriers, a UA may not have a current PUSCH allocationfor a particular reporting carrier. Such a UA would not have thenecessary scheduling information and therefore could not perform the PHcalculation. In an embodiment, the UA makes certain assumptions in thissituation in order to calculate and report PH values for anynon-scheduled carriers. One of three different techniques might be used.

In one technique, the UA copies the resource configuration for ascheduled carrier. At least one carrier must be scheduled in order forthe UA to be able to transmit a PH report. Any non-scheduled reportingcarriers can use the same scheduling configuration (i.e., the number ofresource blocks and the transport block size), as given for a selectedscheduled carrier, in order to calculate a PH value. Possible methodsfor selecting a scheduled carrier whose scheduling configuration wouldbe “copied” could be to select the nearest carrier as measured bycarrier frequency or to select the scheduled carrier with the lowest orhighest carrier frequency.

In another technique, the configuration of the Sounding Reference Signal(SRS) transmission is used. The SRS is transmitted periodically from theUA and is used by the access node to detect the UA channel situation.For frequency-selective scheduling, the access node configures the UA totransmit SRS in each carrier. The number of resource blocks of the SRStransmission is semi-statically configured and Δ_(TF,k)(i) is set tozero, so the UA is typically aware of these values. Since both the UAand access node know the SRS transmission parameters, the number ofresource blocks of the SRS transmission can be used if a PUSCHtransmission is not scheduled for a particular carrier.

In another technique, a reference configuration is predefined. Fixedreference values for the number of resource blocks and the transportblock size can be predefined or configured by higher-layer signaling andthen used in the calculation of a PH value for a non-scheduled carrier.

When the PUSCH and the PUCCH are configured for simultaneoustransmission, the PUCCH-related PH may need to be transmitted toindicate that the transmit power used for the PUCCH-related PH can bethe PH only for the PUCCH or can be a combined PUCCH and PUSCH PH. Ifthe access node receives only the PUSCH PH, it may be difficult toexactly estimate the allowable PUSCH power when the PUSCH and PUCCH aretransmitted simultaneously, because the sum of PUSCH and PUCCH power islimited not to exceed the maximum transmit power. In one embodiment, theUA transmits the PUCCH-related PH in a MAC control element when PHreporting is triggered and a PUSCH resource is scheduled. When the PUCCHis transmitted in the same subframe in which the PUSCH resource isallocated, the PUCCH-related PH is calculated by the UA based on theactual transmit power of the PUCCH. In one embodiment, the calculatedPUCCH-related PH is inserted in the MAC control element and transmittedto the access node. However, it can happen that the PUCCH is nottransmitted when the PUCCH-related PH is reported, because PUCCHtransmission is independent of PUSCH transmission. In this case, the UAcannot calculate the PH because the PUCCH transmit power is not definedwhen the PUCCH is not transmitted. One solution is to assume a referenceconfiguration among different PUCCH formats when the UA transmits thePUCCH-related PH and the PUCCH is not transmitted. This referenceconfiguration can be predefined in the specification or configured byhigher layer signaling. The higher layer signaling could be UA-specificsignaling or broadcast signaling. For example, the referenceconfiguration could be one of the PUCCH formats from 3rd GenerationPartnership Project (3GPP) Technical Specification (TS) 36.211, hereinincorporated by reference. For example, the reference configurationcould be PUCCH format 1A from TS 36.211. In some embodiments, the PUCCHformat requiring the most transmission power is used as the referenceconfiguration. When using a reference configuration, the UA estimatesthe transmission power needed to transmit the PUCCH assuming it were totransmit the PUCCH using the reference configuration. It then uses thisestimated transmission power to calculate the PUCCH-related PH.

For example, the following equation may be used in the two casesdiscussed, with the second equation using PUCCH format 1a as thereference configuration:

${{PH}(i)} = \left( \begin{matrix}{P_{CMAX} - \left\{ {P_{0{\_{PUCCH}}} + {PL} + {h\left( {n_{CQI},n_{HARQ}} \right)} + {\Delta_{F\;\_\;{PUCCH}}(F)} + {g(i)}} \right.} & {{if}\mspace{14mu}{PUCCH}\mspace{14mu}{is}\mspace{14mu}{transmitted}} \\{P_{CMAX} - \left\{ {P_{0{\_{PUCCH}}} + {PL} + {g(i)}} \right\}} & {otherwise}\end{matrix} \right.$

In the previous equation, it is assumed that PH is reported only for thePUCCH. For the combined PUCCH and PUSCH PH case, the following equationcan be used:

${{PH}(i)} = \left( \begin{matrix}\left. \begin{matrix}{P_{CMAX} - \left\{ {P_{0\;\_\;{PUCCH}} + {PL} + {h\left( {n_{CQI},n_{HARQ}} \right)} + {\Delta_{F\;\_\;{PUCCH}}(F)} + {g(i)} -} \right.} \\\left\{ {{10{\log_{10}\left( {M_{PUSCH}(i)} \right)}} + {P_{O\;\_\;{PUSCH}}(j)} + {{\alpha(j)} \cdot {PL}} + {\Delta_{TF}(i)} + {f(i)}} \right\}\end{matrix} \right) & {{if}\mspace{14mu}{PUCCH}\mspace{14mu}{is}\mspace{14mu}{transmitted}} \\\left. \begin{matrix}{P_{CMAX} - \left\{ {P_{0\;\_\;{PUCCH}} + {PL} + {g(i)}} \right\} -} \\\left\{ {{10{\log_{10}\left( {M_{PUSCH}(i)} \right)}} + {P_{O\;\_\;{PUSCH}}(j)} + {{\alpha(j)} \cdot {PL}} + {\Delta_{TF}(i)} + {f(i)}} \right\}\end{matrix} \right) & {otherwise}\end{matrix} \right.$

In another embodiment, the UA assumes the fixed value for the parameterswhich are variable depending on the transmitted PUCCH transmission.According to the equation to set the PUSCH transmission power describedin 3GPP TS 36.213, h(n_(CQI),n_(HARQ)) and Δ_(F) _(—) _(PUCCH)(F) aredifferent for different PUCCH formats. When the PUCCH is nottransmitted, the UA uses reference values for these parameters, wherethe reference value can be predefined in the specification or configuredby higher layer signaling. For example, if the UA assumes bothh(n_(CQI),n_(HARQ)) and Δ_(F) _(—) _(PUCCH)(F) as 0, the above equationcan be used. Other non-zero values can also be used.

FIG. 11 illustrates an exemplary MAC control element wherein the PUSCHPH and PUCCH-related PH are transmitted in a single MAC control element.In FIG. 11, four reserved bits are included in octet 1, six bits areused to represent the PUSCH PH and six bits are used to represent thePUCCH-related PH.

In some embodiments, one MAC control element is used to represent thePUSCH PH and another MAC control element is used to represent thePUCCH-related PH. In some embodiments, if the allocated UL resourcescannot accommodate the combined MAC control element (PUCCH-relatedPH+PUSCH PH) plus its subheader as a result of logical channelprioritization, then the UA only transmits one MAC control elementcontaining the PUSCH PH.

In some embodiments, the access node configures whether PUCCH-related PHreporting should be performed using broadcast signaling or dedicated(UA-specific) signaling. For example, the access node can configure someUAs to report PUCCH-related PH and PUSCH PH. These two reports can betransmitted from the UA using a single MAC control element. The accessnode can configure other UAs to report only PUSCH PH. This one reportcan be transmitted from the UA using a single MAC control element. Theconfiguration can be based on UA capability, scheduling algorithms, etc.

Combinations of the above embodiments can also be used. For example, aUA may be configured to report PUSCH PH for one or multiple carriers andPUCCH-related PH for one or multiple carriers. One or multiple MACcontrol elements can be used to report the required PH information.

As mentioned above, one of the factors included in the calculation ofpower headroom is the downlink path loss. When multiple downlinkcomponent carriers are aggregated, it may not be clear which of thedownlink component carriers is to be used for deriving path loss andthus for deriving the power headroom. For example, it may not bedesirable to calculate path loss on a downlink component carrier thathas been deactivated. In an embodiment, two alternatives are providedfor determining which downlink component carrier is to be used forderiving path loss. In one alternative, the determination of whichdownlink component carrier is to be used for path loss derivation isbased on a downlink component carrier that is linked to an uplinkcomponent carrier in the broadcast system information. In anotheralternative, the determination of which downlink component carrier is tobe used for path loss derivation is based on a downlink componentcarrier that that has been designated for path loss derivation.

Details of how to derive the path loss (PL) value in a carrieraggregation scenario are now provided. The PL value is required tocalculate the PH value at uplink carriers as shown in the followingequation.PH _(k)(i)=P _(CMAX,k)−{10 log₁₀(M _(PUSCH,k)(i))+P _(O) _(—)_(PUSCH,k)(j)+a_(k)(j)·PL _(k)+Δ_(TF,k)(i)f _(k)(i)}

PL is the downlink path loss estimate derived by the UA, andPL=referenceSignalPower−higher layer filtered RSRP (Reference SignalReceived Power), where referenceSignalPower is provided by higher layersand RSRP is measured in the UA and filtered with the higher layer filterconfiguration defined by higher layers.

Since only one DL Component Carrier (CC) and one UL CC are supported inRelease-8, it is preferable that PL be derived from the DL CC on whichthe UA measures RSRP. In carrier aggregation, however, a UA can beconfigured to receive multiple DL CCs, and it may be possible to referto any DL CC for path loss derivation, although there is a cell-specificlinkage between DL CC and UL CC for idle mode UAs, and this linkage istypically signaled in the system information. Therefore, it may behelpful to define which of the multiple DL CCs should be used for PLderivation.

There are two aspects to be considered when defining the UA operation todetermine the DL CC to be used for PL derivation. In the first aspect,the DL CC may not always be activated. In carrier aggregation, multipleDL CCs may be configured for a UA supporting carrier aggregation. Theseconfigured DL CCs can be activated or deactivated via MAC signaling.Actual downlink data is scheduled only to the activated DL CCs. Thismeans that the UA may not need to receive PDCCH or PDSCH on thedeactivated DL CCs. In this case, to save UA battery power, the UA couldstop receiving all DL transmissions on the deactivated DL CCs. If the UAis implemented in this way, it would also be desirable not to derive PLon a deactivated CC even though that DL CC has been designated for PLderivation (especially if RSRP measurement on a deactivated CC consumesUA processing power). One exception would be that the UA could measureRSRP on a deactivated CC if this measurement is explicitly configured byhigher layer signaling.

In the second aspect, a different DL CC can be used other than thelinked DL CC for PL derivation. To compensate for the difference betweenthe PL derived with a different DL CC and the actual PL for PHcalculation of a UL CC, an offset value can be signaled by the accessnode. The access node could generate this offset based on measurementreporting or a statistical model or field testing. However, the PL maynot be correct in the actual environment, especially if the DL CC beingreferenced is located in a different frequency band from the UL CC andthe UA is moving.

To clarify the description of the proposed UA operation for PLderivation, the following carrier types are introduced. One type can bereferred to as the Downlink Primary Component Carrier (DL PCC). In thiscase, one of the DL CCs is configured as the DL PCC, and the DL PCC isnever deactivated. Another type can be referred to as the Paired DL CC.This is a DL CC cell specifically linked to a UL CC in the broadcastsystem information. Another type can be referred to as the DL CC_pl.This is a DL CC used for PL derivation. Each UL CC could be configuredto reference one DL CC_pl for PL derivation. With these definitions inplace, two alternatives can be provided.

In the first alternative, the UA uses the paired DL CC for PL derivationif that paired DL CC is activated or configured for measurement. Sincethe paired DL CC for each UL CC is signaled in the system information,additional signaling to indicate DL CC_pl would not be required. Whenthe paired DL CC is deactivated and has not been configured formeasurement, and the UL CC still needs to be transmitted, there arethree possible approaches. In a first approach, the UA may still derivePL from the (deactivated) paired DL CC. In this case, the UA stillmeasures RSRP on the paired DL CC. In a second approach, the UA mayderive PL from another DL CC in the same band where the other DL CC isactivated or where measurement has been configured. In a third approach,the UA derives PL from another DL CC provided by the access node. Thereference carrier may be implicit, such as the DL PCC. The offsetbetween DL CCs and PCC may need to be signaled. Since PL difference islikely to happen when PCC and DL CC are in different bands, the offsetcan be signaled if the corresponding DL CC is in a different band thanPCC. Alternatively, the offset between frequency bands can be signaled.

One of these approaches can be selected or all three approaches can bedefined. When all approaches can be applicable, it may be preferable toprioritize using the first or second approach, considering the accuracyof PL derivation. In other words, if the paired DL CC is not activatedand not configured for measurement, the UA may still derive PL from thepaired DL CC or may derive PL from another DL CC in the same band wherethe DL CC is either activated or measurement is configured. Otherwise,the UA might use the offset (and the reference DL CC where the offsetshould be applied) provided by the access node.

In a second alternative, the access node can configure the UA toreference any DL CC for DL CC_pl. An offset may not be needed if the PLof DL CC_pl and the actual PL required for the UL CC are similar. Thismight happen if they are located in the same frequency band. Otherwise,the offset could be signaled. Two different UA operations might be useddepending on whether the DL CC_pl is in the same frequency band as theUL CC or not. In the case where DL CC_pl is in the same frequency bandas the UL CC, the UA could use the DL CC_pl for PL derivation if that DLCC_pl is activated or configured for measurement. When DL CC_pl isdeactivated but the UL CC still needs to be transmitted, the UA couldapply the same approaches as described with regard to the firstalternative. In the case where DL CC_pl is in a different frequencyband, the UA may use another DL CC, e.g., the paired DL CC or DL CC inthe same frequency band with the UL CC if this DL CC is activated orconfigured for measurement. Otherwise, the UA could derive the PL withDL CC_pl and an offset. This is because the PL derived by the paired DLCC or DL CC in the same frequency band might be more accurate than thePL derived by the DL CC_pl with an offset. The same PL derivation methodcould be applied to the uplink transmit power setting for uplinkchannels, e.g., PUSCH or PUCCH, as well as the PH value calculation ineach UL CC.

FIG. 12 illustrates an embodiment of a method 1200 for reporting powerheadroom-related information for a plurality of aggregated carriers. Atblock 1210, power headroom-related information is reported for a numberof the aggregated carriers that is less than or equal to the totalnumber of aggregated carriers.

The UA 210, the access node 220, and other components described abovemight include a processing component that is capable of executinginstructions related to the actions described above. FIG. 13 illustratesan example of a system 1300 that includes a processing component 1310suitable for implementing one or more embodiments disclosed herein. Inaddition to the processor 1310 (which may be referred to as a centralprocessor unit or CPU), the system 1300 might include networkconnectivity devices 1320, random access memory (RAM) 1330, read onlymemory (ROM) 1340, secondary storage 1350, and input/output (I/O)devices 1360. These components might communicate with one another via abus 1370. In some cases, some of these components may not be present ormay be combined in various combinations with one another or with othercomponents not shown. These components might be located in a singlephysical entity or in more than one physical entity. Any actionsdescribed herein as being taken by the processor 1310 might be taken bythe processor 1310 alone or by the processor 1310 in conjunction withone or more components shown or not shown in the drawing, such as adigital signal processor (DSP) 1380. Although the DSP 1380 is shown as aseparate component, the DSP 1380 might be incorporated into theprocessor 1310.

The processor 1310 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 1320,RAM 1330, ROM 1340, or secondary storage 1350 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one CPU 1310 is shown, multiple processors may bepresent. Thus, while instructions may be discussed as being executed bya processor, the instructions may be executed simultaneously, serially,or otherwise by one or multiple processors. The processor 1310 may beimplemented as one or more CPU chips.

The network connectivity devices 1320 may take the form of modems, modembanks, Ethernet devices, universal serial bus (USB) interface devices,serial interfaces, token ring devices, fiber distributed data interface(FDDI) devices, wireless local area network (WLAN) devices, radiotransceiver devices such as code division multiple access (CDMA)devices, global system for mobile communications (GSM) radio transceiverdevices, worldwide interoperability for microwave access (WiMAX)devices, and/or other well-known devices for connecting to networks.These network connectivity devices 1320 may enable the processor 1310 tocommunicate with the Internet or one or more telecommunications networksor other networks from which the processor 1310 might receiveinformation or to which the processor 1310 might output information. Thenetwork connectivity devices 1320 might also include one or moretransceiver components 1325 capable of transmitting and/or receivingdata wirelessly.

The RAM 1330 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 1310. The ROM 1340 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 1350. ROM 1340 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 1330 and ROM 1340 istypically faster than to secondary storage 1350. The secondary storage1350 is typically comprised of one or more disk drives or tape drivesand might be used for non-volatile storage of data or as an over-flowdata storage device if RAM 1330 is not large enough to hold all workingdata. Secondary storage 1350 may be used to store programs that areloaded into RAM 1330 when such programs are selected for execution.

The I/O devices 1360 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input/output devices. Also, thetransceiver 1325 might be considered to be a component of the I/Odevices 1360 instead of or in addition to being a component of thenetwork connectivity devices 1320.

In an embodiment, a method is provided for reporting powerheadroom-related information for a plurality of aggregated carriers. Themethod includes reporting in a bitmap the power headroom-relatedinformation for a number of the aggregated carriers that is less than orequal to the total number of aggregated carriers, wherein the powerheadroom-related information is one of a power headroom for at least oneof the aggregated carriers and a path loss for at least one of theaggregated carriers.

In another embodiment, a user agent is provided. The user agent includesa component configured such that the user agent transmits in a bitmappower headroom-related information for a number of aggregated carriersthat is less than or equal to the total number of aggregated carriers ina plurality of aggregated carriers, wherein the power headroom-relatedinformation is one of a power headroom for at least one of theaggregated carriers and a path loss for at least one of the aggregatedcarriers.

In another embodiment, an access node in a wireless telecommunicationssystem is provided. The access node includes a component configured suchthat the access node receives in a bitmap power headroom-relatedinformation for a number of aggregated carriers that is less than orequal to the total number of aggregated carriers in a plurality ofaggregated carriers, wherein the power headroom-related information isone of a power headroom for at least one of the aggregated carriers anda path loss for at least one of the aggregated carriers.

In another embodiment, a method is provided for reporting powerheadroom-related information for a plurality of aggregated carriers. Themethod comprises reporting the power headroom-related information for anumber of the aggregated carriers that is less than or equal to thetotal number of aggregated carriers, wherein the power headroom-relatedinformation is one of a power headroom for at least one of theaggregated carriers and a path loss for at least one of the aggregatedcarriers. The method or portions of the method may be carried out by aUA and/or an access node.

In another embodiment, a method is provided for reporting power headroomfor a plurality of aggregated carriers. The method comprisestransmitting a power headroom value that is one of a power headroom fora reference carrier in the aggregation of carriers and a function ofpower headroom values for the aggregation of carriers. The methodfurther comprises, for each of the remaining carriers in the aggregationof carriers, reporting a variation of the power headroom from thetransmitted power headroom value. The method or portions of the methodmay be carried out by a UA and/or an access node.

In another embodiment, a method is provided for determining whichcarrier among a plurality of aggregated carriers is to be used forderivation of a path loss. The method comprises basing the determinationon at least one of a downlink component carrier that is linked to anuplink component carrier in broadcast system information and a downlinkcomponent carrier that has been designated for path loss derivation. Themethod or portions of the method may be carried out by a UA and/or anaccess node.

The following are incorporated herein by reference for all purposes: 3rdGeneration Partnership Project (3GPP) Technical Specification (TS)36.211, 3GPP TS 36.213, 3GPP TS 36.321, and 3GPP Technical Report (TR)25.942.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the scopeof the present disclosure. The present examples are to be considered asillustrative and not restrictive, and the intention is not to be limitedto the details given herein. For example, the various elements orcomponents may be combined or integrated in another system or certainfeatures may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A method for reporting power headroom-relatedinformation for aggregated carriers, comprising: reporting in a mediaaccess control (MAC) control element power headroom-related informationfor a number of the aggregated carriers that is less than or equal tothe total number of aggregated carriers; reporting in the MAC controlelement a bitmap, each aggregated carrier corresponding to a bit in thebitmap, one value in the bitmap indicating that the powerheadroom-related information for a corresponding carrier is beingreported, and another value in the bitmap indicating that the powerheadroom-related information for a corresponding carrier is not beingreported; and receiving power control commands for a plurality of theaggregated carriers.
 2. The method of claim 1, wherein the powerheadroom-related information is power headroom information.
 3. Themethod of claim 1, wherein the power headroom-related information ispath loss information.
 4. The method of claim 1, wherein each carrier isassociated with a carrier index.
 5. The method of claim 1, wherein thereporting of the power headroom-related information is triggered by oneof: a change in the path loss of a reporting carrier among theaggregation of carriers greater than a pre-defined amount since aprevious power headroom report; addition of a carrier to the aggregationof carriers; and expiration of a timer that controls periodic powerheadroom reports.
 6. The method of claim 1, wherein the powerheadroom-related information is reported as a result of one of: adifference in path loss between consecutive measurements of path lossfor one of the carriers exceeding a threshold; a transmission on acarrier's physical uplink shared channel being scheduled; and a powerheadroom for a carrier exceeding a threshold.
 7. The method of claim 1,wherein a physical uplink control channel (PUCCH)-related power headroomis transmitted in the MAC control element when power headroom reportingis triggered and a physical uplink shared channel (PUSCH) resource isscheduled.
 8. The method of claim 7, wherein, when the PUCCH istransmitted in the same subframe in which the PUCCH-related powerheadroom is reported, the PUCCH-related power headroom is calculatedbased on an estimated transmit power of the PUCCH.
 9. The method ofclaim 1, wherein the bitmap includes at least five bits.
 10. A useragent (UA), comprising: a processor; and a computer readable mediumconfigured to store instructions such that when executed by theprocessor, the UA transmits in a media access control (MAC) controlelement power headroom-related information for a number of aggregatedcarriers that is less than or equal to the total number of aggregatedcarriers, and wherein the UA transmits in the MAC control element abitmap, each aggregated carrier corresponding to a bit in the bitmap,one value in the bitmap indicating that the power headroom-relatedinformation for a corresponding carrier is being transmitted, andanother value in the bitmap indicating that the power headroom-relatedinformation for a corresponding carrier is not being transmitted,wherein the computer readable medium is further configured to storeinstructions such that when executed by the processor, the UA receivespower control commands for a plurality of the aggregated carriers. 11.The UA claim 10, wherein the power headroom-related information is powerheadroom information.
 12. The UA of claim 10, wherein the powerheadroom-related information is path loss information.
 13. The UA ofclaim 10, wherein each carrier is associated with a carrier index. 14.The UA of claim 10, wherein the transmitting of the powerheadroom-related information is triggered by one of: a change in thepath loss of a reporting carrier among the aggregation of carriersgreater than a pre-defined amount since a previous power headroomreport; addition of a carrier to the aggregation of carriers; andexpiration of a timer that controls periodic power headroom reports. 15.The UA of claim 10, wherein the power headroom-related information istransmitted as a result of one of: a difference in path loss betweenconsecutive measurements of path loss for one of the carriers exceedinga threshold; a transmission on a carrier's physical uplink sharedchannel being scheduled; and a power headroom for a carrier exceeding athreshold.
 16. The UA of claim 10, wherein a physical uplink controlchannel (PUCCH)-related power headroom is transmitted in the MAC controlelement when power headroom reporting is triggered and a physical uplinkshared channel (PUSCH) resource is scheduled.
 17. The UA of claim 16,wherein, when the PUCCH is transmitted in the same subframe in which thePUCCH-related power headroom is reported, the PUCCH-related powerheadroom is calculated based on an estimated transmit power of thePUCCH.
 18. The UA of claim 10, wherein the bitmap includes at least fivebits.